Ok so when I put in my new transmission I cut out the cats since it was all ripped apart. I now have sims and everything works great with the slip fit pipes. Everything is welded and not leaking. When the motor is under a lot of load there is a rattle that is coming from the muffler. A friend of the family works at an exhaust shop and has told me it is the internal parts of muffler that is causing the rattle. I have a cutout about halfway back and when it is open it rattles louder and when it is closed it rattles more quietly. Either way I need to find a new muffler that can handle the pressure coming from the motor because of the fact that I have no cats. Has anyone done this and if so can you give me some pointers. Thanks a lot.

Adam